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Letters : Up in smoke

Kurt Kleiner reports that 88 per cent of Americans have traces of nicotine in
their blood, supposedly caused by exposure to environmental tobacco smoke and
measured by cotinine analysis (This Week, 4 May, p 9).

The use of cotinine as a measure of such exposure is open to doubt. In the
New England Journal of Science (August 1993), Edward Domino reported that one
microgram of nicotine would be absorbed by consuming the following amounts of
common vegetables: 8 ounces of ripe tomatoes, 2.5 oz of green tomatoes, 5 oz of
potatoes, 1.5 oz of puréed potatoes, 2 oz of cauliflower, 0.25 oz of
aubergine.

Ruth Etzel has also questioned the reliability of cotinine as an indicator of
exposure (Preventive Medicine, vol 19, 1990), noting that high levels
of cotinine had been found in people not exposed to tobacco smoke, a finding
noted in the present work.

It is also worth noting that the 1993 report by the US Environmental
Protection Agency quoted by Kleiner caused a furore amongst American scientists
because of its highly selective use of data. Its findings were based on 11
American studies while ignoring some 19 other studies not of US origin, it used
meta-analysis which ignored virtually all accepted rules for combining results
in such studies and it used 90 per cent confidence limits rather the generally
accepted 95 per cent limits which, incidentally, would have shown no significant
risk.

Similarly, the work on chickens was criticised because of the unrealistically
high exposure levels, some of the early work being equivalent to a daily
consumption of millions of cigarettes a day.

It is stated that the new study shows that almost everyone is exposed to
cigarette smoke every day. This is difficult to reconcile with the statement
that more than half of the people studied neither work nor live with
smokers.

In 1990, an American epidemiologist admitted: “Yes, it’s rotten science, but
it’s a worthy cause.” Six years later, things have hardly changed.